BillThompson.us

This page has been updated for 2019 to reflect some changes and refinements to the digital controller.

The project started when I acquired a Thorens TD-124 turntable. This is a great Swiss made turntable from the 1950’s featuring a heavy platter, very precise bearings, and a number of nice features, my favorite of which is the clutch that lets you stop the rotation to load and unload records. It also has a very pretty art-deco design. Its become quite collectible.

To me the weak link on this turntable is the motor. I replaced it with a high quality DC motor/tachometer and designed a motor controller for it.

This isn’t exactly new. I started this preamp project when I was just getting into digital recording in 2001 and still very active in Ashly Audio but I’m still using these preamps unmodified to this day. I wanted a very clean, neutral preamp with absolutely no unnecessary bells and whistles.

I have a couple of older Dynaco PAS-3 preamps around. I used to enjoy the sound of these preamps many years ago but a few issues have kept me from using them these days. I tried to tackle the biggest problems using parts I had around.

For a long, long time, probably forty years, I’ve owned a moderate size sound system that I occasionally used indoors and outdoors at various concerts and folk festivals. The low end is a pair of EAW “Forsythe” cabinets each containing a pair of JBL 2220 woofers, The midrange is a big muticellular horn with a JBL 2445 2 inch driver, the high end is an Altec Lansing 511-B horn with a JBL 2425 1 inch driver and an added JBL 2405 supertweeter. This was nice and efficient but it never did a good job on the lowest octave. I needed subwoofers.

I recently came upon a pair of Schoeps CMC-4U microphone amplifier bodies. These look just like the common CMC-5U’s but they use a different powering system called T-Power and won’t work with modern preamps. I wondered if it would be possible to modify the CMC-4 so it could use standard phantom power like the CMC-5.

This all started when I was about 12 years old. Our neighbors had this cool 1941 Philco console radio in their attic, I was fascinated by radios and record players, and they let me mess with it. It had a record player with Philco’s “Beam of Light” system for the phono pickup, I took it apart to see how it worked, and was fascinated by it. Fast-forward about 60 years and I found a console with this record player, bought it, and set about restoring it.